1. Field of the Invention
The present invention relates generally to an electrical assembly and more particularly to an assembly for shielding an electronic circuit disposed on a substrate from interference.
2. Description of the Related Art
Modern electronic equipment includes electrical circuits mounted on a substrate that are sensitive to electromagnetic interference (EMI) and radio frequency interference(RFI) (collectively, interference). Interference may originate from internal sources within the electronic equipment or from external interference sources. Interference can cause degradation or complete loss of important signals, rendering the electronic equipment inefficient or inoperable.
To minimize interference, electrically conducting material is interposed between portions of the electrical circuit. For manufacturability purposes, this material is tooled into multiple enclosures or shields that conform to the electrical circuits. These shields are attached, typically via soldering, to grounded traces positioned both on the substrate and around the electrical circuits generating the interference as well as around the electrical circuits that are susceptible to interference. Oftentimes, the shields are attached in adjacency.
Techniques for adjacently attaching such shields include providing dual traces (a separate trace for each shield) and providing a single trace that is shared by both shields. However, dual traces consume an unacceptable amount of physical space. For example, assuming that each trace is 1.00 mm wide and each trace is separated by a 0.26 mm gap to ensure reliable attachment, dual traces require at least 2.26 mm of substrate area. Unfortunately, a single, shared trace has been found to be too unreliable. During attachment of the shields to a shared trace, such as the aforementioned 1.00 mm trace, the solder exhibits capillary attraction and migrates from the trace onto one or both shields. This leaves an insufficient amount of solder at the trace-shield interconnection thereby preventing reliable attachment. When sharing a trace as such the shields also tend to skew and even walk off the trace during attachment.
As portable electronic equipment becomes increasingly miniaturized and components of electrical circuits are placed closer together, the physical room available for shielding is greatly reduced. Therefore, what is needed is a shield assembly and a method of shielding that consumes as little space as possible and provides secure, reliable, and easily manufacturable interconnections.